Desempenho e perfil de ácidos graxos do leite de vacas alimentadas com óleo de girassol em dietas à base de cana-de-açúcar

• Autor(a) principal: Souza, Shirley Motta de
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1783
• topic: Desempenho; Digestibilidade; Óleo; Vacas de leite; Performance; Digestibility; Oil; Dairy cows; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL

Two experiments were carried out at Embrapa Dairy Cattle in order to evaluate the effects of sugar cane-based diets containing different levels of sunflower oil (0, 1.5, 3.0 and 4.5% of diet DM) on performance and milk fatty acid composition of dairy cows. In Experiment 1, twelve multiparous Holstein x Gir cows in milk and average milk production of 17±5 kg/d) received the four dietary treatments (levels of sunflower oil inclusion, % of diet DM) in a triplicate 4 x 4 Latin Square design balanced for residual effect. Each experimental period lasted 16 days, being 10 d for adaptation and the last 6 d for data collection. During the collection period, milk samples were obtained daily from morning and afternoon milking and analyzed for major components (fat, protein and lactose) as well as urea and alantoin contents. Additionally, blood and milk samples were collected on the last day of each experimental period, frozen at -20 o C and analyzed for plasma metabolites and fatty acid profile, respectively. The production of faecal dry matter was estimated from samples collected during six consecutive days using indigestible NDF as an internal indicator. There was no effect of dietary treatments on DM intake, milk production (corrected or not for 3.5% fat), milk protein and milk lactose content. However, milk fat content and yield as well as total solids content and microbial protein production were linearly reduced as the level of sunflower oil in the diet increased from 0 to 4.5%. On the other hand, blood concentrations of NEFA, total cholesterol and triglycerides were positively associated with the level of sunflower oil in the diet. The concentrations of short and medium chain fatty acids in milk fat were linearly reduced as the level of sunflower oil increased, whereas total unsaturated fatty acids and CLA in milk fat were increased. In Experiment 2, four multiparous Holstein x Gir cows with cannulas in the rumen were used in a balanced 4 x 4 Latin Square design composed of 19-day experimental periods (10 d for adaptation and the last 9 d for data collection). Milk and blood samples were collected during the last 9 days of each experimental period as described in the Experiment 1, and then analyzed for the same components. The production of faecal dry matter was also estimated from samples collected during six consecutive days using indigestible NDF as an internal indicator. Dry matter intake, milk production, milk composition (including milk fatty acid profile) and production of microbial protein were affected the same way as observed in the Experiment 1. Sunflower oil did not alter the flow of DM, OM, CP and NDFap. The cows fed sunflower oil had higher levels of C18:1 trans-4, C18:1 trans 6-8, C18:1 trans-9, C18:1 trans-10, C18:1 trans-11, C18:1 trans-12, C18:1 trans-12 and trans-13, as well as higher levels of C18:1 cis-13 and C18:1 trans-16 in the canal of the omasum. Concentrations of total cholesterol and HDL in blood increased as the level of sunflower oil in the diet increased from 0 to 4.5%. Dry matter and NDF digestibility, pH and concentrations of NH3 and VFA in the rumen were unaffected by dietary treatments. It can be concluded that the inclusion of sunflower oil into sugar cane-based diets reduces the concentration of hypercholesterolemic medium chain saturated fatty acids and increases the concentration of health-promoting polyunsaturated fatty acids such as cis-9 trans-11 CLA in milk fat from Holstein x Gir dairy cows, which could be beneficial to human health. However, the reduction in milk fat content observed in cows fed diets containing sunflower oil would be disadvantageous in payment systems based on milk solids content. Therefore, this adverse response should be weighed against the potential benefits of producing milk with enhanced nutraceutical properties.